Apparatus for length stabilization of a cable

ABSTRACT

Apparatus for the length stabilization of armored well logging cable. The cable is passed from a payoff reel over hold back sheaves, a series of fixed sheaves, a movable sheave, and haul off sheaves to a take-up reel. A hydraulic system controls the movable sheave to place the cable under tension. A second hydraulic system cyclically varies the effect of the hold back sheaves to vary the cable tension.

O United States Patent 1191 1111 3,871,205 Fenton 1451 Mar, 18, 1975 1 APPARATUS FOR LENGTH 2,843,881 7/1958 Bishop et a1. 28/713 x STABILIZATION O A CABLE 2,940,883 6/1960 Peirce 219 /155 X 3,084,393 4/1963 Rodenacker 28/713 UX [75] Inventor: G. Donald Fenton, t Mass- 3,153,696 10/1964 Blanchard... 72/378 x 3,319,411 5/1967 Rice 57/555 X [73] Assgnee' P' states steelcmpm'amn 3,397,721 8/1968 Lovelett 72/183 x Plttsburg, 3,548,624 12/1970 Hann et a1. 72/183 1 FiledI May 1973 v FOREIGN PATENTS OR APPLICATIONS [21] App]. No.: 362,611 710,708 6/1954 United Kingdom 28/713 Related U 8 Application Dam 371,910 5/1932 United Kingdom 28/713 [63] Continuation of Ser. No. 168,935, Aug. 4, 1971. primary Examiner RichaI-d J. Herbst Assistant Examiner-D. M. Gurley [52] US. Cl 72/128, 72/183, 72/378, Attorney, Agent, or p C Helm 219/7.5, 226/195, 57/555, 28/595, 19/242 [51] lnt. Cl B211 9/00 [58] Field of Search 29/446, 452; 74/231 R, [57] ABSTRAFT 74/231 M; 72/l7, 128, 205 288, 378, Apparatus for the length stablllzation of armored well 219,75 153, 57/555; 28/595 713 logging cable. The cable 18 passed from a payoff reel 714, 7217; 19/242; 226/195 over hold back sheaves, a series of fixed sheaves, a movable sheave, and haul off sheaves to a take-up [56] References Cited reeLlA hyglraultijci systgm controls :16 mOVZbLE Shealve o pace e ca e un er ens1on. secon y rau 1c 2 214 709 E Q PATENTS 57/55 5 system cyclically varies the effect of the hold back es 111 2,389,292 11/1945 Bjorksten 28/713 ux Sheaves to Vary the cable 2,771,635 11/1956 Munch 28/71.3 X 6 Claims, 3 Drawing Figures ELECTR/CAL HEAT/N6 SYSTEM PATENTEDHARTB ms 3.87 1 .205

' SHEIZIEZ FIG. 2.

APPARATUS FOR LENGTH STABILIZATION OF A CABLE This is a continuation of application Ser. No. 168,935, filed Aug. 4, 1971.

This invention relates to apparatus for improving the length stability of a cable and more particularly, to apparatus for intermittent loading of an armored lossing cable during a prestressing operation.

In oil well logging operations, it is important that the length of the logging cable be known precisely, or, if it changes, that the rate of change be known within close limits. Temperature and tension affect cable length in a predictable way provided the cable does not continue to elongate appreciably in use. When such elongation occurs, the cable is not suitable for measuring depths within useful limits.

Logging cables are prestressed before use at a load substantially below the yield point toremove the initial stretch present in an unstressed cable. Hence, manufacturers prestress or preload a cable before shipment. This prestressing may be with or without the application of heat. Blanchard Pat. No 3,153,696, dated Oct. 20, 1964; Pierce Pat. No. 2,940,883, dated June 14, 1960; and Pierce Pat. No. 2,952,574, dated Sept. 13, 1960, teach that the use of heat in a prestressing operation improves cable length stability. Similarly, cable may be oven baked under tension on a reel to achieve a like result. In either case, the temperature is kept below the melting point of the insulation to avoid damage to the conductors. Both methods have been used to reduce further stretch of the cable in service.

However, it has been demonstrated that not all cables subjected to a single loading or tensioning have sufficient of the non-recoverable stretch removed to fully satisfy the needs in service. Additional applications of stress to the cable further reduce the stretch. Obviously, multiple stressing operations are costly and increase the dangers of cable damage. In addition, cables that are oven baked on a reel may be flattened to a considerable extent.

In accordance with my invention, I provide apparatus to cyclically load a cable during a prestress operation while simultaneously providing the means for optional heating of the cable.

It is therefore an object of my invention to provide apparatus for stabilizing the length of a cable by cyclically loading during prestressing.

Another object is to provide such apparatus that does not deform the cable.

Still another object is to provide such apparatus that simultaneously heats the cable.

These and other objects will become more apparent after referring to the following specification and drawings in which: i

FIG. 1 is a side elevational view of the prestressing equipment;

FIG. 2 is a schematic diagram of the cycling and holdback system; and

FIG. 3 is a diagrammatic top plan view of the loading system.

Referring now to the drawings in which FIG. 1, together with parts of FIGS. 2 and 3, is the apparatus shown in Pierce Pat. No. 2,940,883, reference numeral 2 indicates an armored electrical oil well logging cable which is to be length stabilized. Cable 2 passes from a payoff reel 4 over a sheave 6 to a pair of capstan sheaves 8 having a number of grooves therein so that cable 2 passes around the sheaves a plurality of times. From sheaves 8, the cable passes successively around a series of sheaves l0, l2, 14, 16, 18, 20, 22, and 24 to a second pair of capstan sheaves 26, power driven and similar to sheaves 8, and then to a motor-driven takeup reel 28 having an overriding friction drive. Sheaves 10, 12, 14, l6, 18, 20, and 22 are mounted on a supporting structure 30.

Sheave 24 is attached to a yoke 32 which is, in turn, attached to a guide 34 (FIG. 3). Guide 34 has a hole 36 on each end adapted to slide along a pair of guide rods 38. Guide rods 38 are each attached to an end frame 40 which is fixed in relation to supports 30. A rack 42 is mounted on guide 34. Rack 42 engages a pinion 46 which turns a potentiometer 48 as guide 34 moves along guide rods 38. Potentiometer 48 is connected to an electrically operated control valve 50 through connection 52 so that the position of guide 34 controls the setting of valve 50. A push rod 54 is atvtached to yoke 32. Push rod 54 is attached to a piston 56 of an hydraulic cylinder 58 which is attached to end frame 40.

Hydraulic fluid from a supply tank 60 is pumped by a first hydraulic pump 62 through a first adjustable pressure relief valve 64 which controls fluid pressure on piston 56 of cylinder 58 through a four-way valve 66. Control valve 50 is connected to bypass hydraulic fluid from valve 64 to tank 60, depending upon the position of piston 56. A gage 68 is connected to indicate pressure in the right chamber of cylinder 58.

Capstan 8 is connected through gearing 70 and a gear box 72 in a step up fashion to drive a second hydraulic pump 74 as shown in FIG. 2. Fluid for pump 74 is supplied from a second supply tank 76 and passes through a filter 78. A second adjustable relief valve 80 sets the pressure on pump 74 to determine the hold back capability of capstan 8. An electrically driven, slow speed gear motor 82 operates a cycling valve 84 through a cam'and cam follower 86 in cyclic fashion at a rate determined by the speed of gear motor 82 to bypass relief valve 80 and send hydraulic fluid back to tank 76. Pressure of the system is indicated on a gage 88 connected to valve 80.

Sheaves l0 and 14 are electrically insulated from frames 30 and are connected to an electrical heating system 90 as described in the Pierce patent.

In operation, valve 80 is set for the desired maximum hold back effect to be exerted on the cable during a cycle which will be inidcated on gage 88. Valve 64 is set so that it will open at a predetermined pressure so that the pressure in cylinder 58 cannot exceed that necessary for applying the desired maximum tensional force to cable 2. Cable 2 is threaded from payoff reel 4 through the line around sheaves 8 in a series of figure eights, around sheaves 10, 12, 14, 16, 18, 20, 22, and 24 in turn and around sheaves 26 in a series of figure eights to take-up reel 28. The friction of cable 2 passing around sheaves 8 drives oil pump 74 and causes it to build up a pressure in the hydraulic fluid so as to apply back tension into the cable as it is moving forward. Assuming that cam 86 is in the position to set valve 84 to provide the maximum hold back effect, pump 62 builds up hydraulic pressure through valves 64 and 66 to move sheave 24 to provide the desired tension. Potentiometer 48, acting through valve 50 varies the hydraulic pressure entering valve 66 so the tension is maintained as the cable stretches. When gear motor 82 has moved cam 86 to change valve 84 to provide the minimum hold back effect, the tension in the cable is reduced tending to movepiston 56 to the left. This actuates potentiometer 48 to move piston 56 back to the right to a neutral position at the minimum hold back effect.

When gear motor 82 returns cam 86 to set valve 84 to per thousand feet. A second prestressing at 180F will typically reduce this elongation to about 2' to 3 feet per thousand feet. When cyclically loaded from 2500 lbs.

- to 10,000 lbs. at a rate of 4'to 7 cycles per minute at a speed of about 75 feet per minute with about 450 feet of cable between capstans 8 and 26, the stretch is reduced to 1.5 to 2.0 feet per thousand feet whether done hot or at room temperature. At this speed each'portion of the cable is exposed to from about to about 40 tensioning cycles.

While one embodiment of my invention has been shown and described, it will be apparent that other modifications and adaptions may be made.

I claim:

1. In an apparatus for length stabilizing a length of cable which apparatus comprises a pair of hold-back sheaves for providing a braking effect, a pair of pulling sheaves, means for driving said pulling sheaves, a series of intermediate sheaves between said hold-back sheaves and said pulling sheaves, said sheaves defining a path through which a cable may travel through the apparatus and one of said intermediate sheaves being mounted for applying tension to the cable between the hold-back sheaves and the pulling sheaves, the combination therewith of means connected to said hold-back sheaves for alternately increasing and decreasing the braking effect of said hold-back sheaves between a maximum level and a minimum level in timed cycles and means connected to one of said intermediate sheaves for applying tension and responsive to saidchange in braking effect for tensioning said cable between maximum and minimum levels whereby each increment of cable length is tensionedthrough a multiplicity of cycles.

2. Apparatus according to claim 1 in which said means for alternately increasing and decreasing the braking effect includes a hydraulicsystem connected to act as a brake on said hold-back sheaves and a cycling valve connected in said system for cyclically changing the pressure in said system.

3. Apparatus according to claim 2 in which said means connected to the sheave for applying tension includes a first supply tank, a first hydraulic pump connected to said supply tank, a first relief valve connected to said first hydraulic pump, a hydraulic cylinder connected to said pump and having a piston connected to said tensioning sheave and mounted for movement in said cylinder, a four-way valve connected to said hydraulic cylinder, said first supply tank and said first relief valve, a potentiometer mounted to be set by movement of said piston, a control valve actuated by said potentiometer and connected between said first supply tank and the connection between the first relief valve and the four-way valve.

4. Apparatus according to claim 3 in which said hydraulic system includes a second supply tank, a second hydraulic pump connected to said secondsupply tank and driven by rotational movement of said hold-back sheaves, a second relief valve connected to said second pump for providing said braking effect, and in which said cycling valve is connected to said second relief valve for cyclically by-passing said second relief valve thereby changing the braking effect.

5. Apparatus according to claim 4 which includes a cam, a gear motor connected to said cam for rotating the cam and a cam follower on said cycling valve adapted to set the position of said cycling valve as said cam rotates.

6. Apparatus according to claim 1 which includes means for applying heat to that part of said cable between a pair of sheaves in said series of intermediate 

1. In an apparatus for length stabilizing a length of cable which apparatus comprises a pair of hold-back sheaves for providing a braking effect, a pair of pulling sheaves, means for driving said pulling sheaves, a series of intermediate sheaves between said hold-back sheaves and said pulling sheaves, said sheaves defining a path through which a cable may travel through the apparatus and one of said intermediate sheaves being mounted for applying tension to the cable between the hold-back sheaves and the pulling sheaves, the combination therewith of means connected to said hold-back sheaves for alternately increasing and decreasing the braking effect of said hold-back sheaves between a maximum level and a minimum level in timed cycles and means connected to one of said intermediate sheaves for applying tension and responsive to said change in braking effect for tensioning said cable between maximum and minimum levels whereby each increment of cable length is tensioned through a multiplicity of cycles.
 2. Apparatus according to claim 1 in which said means for alternately increasing and decreasing the braking effect includes a hydraulic system connected to act as a brake on said hold-back sheaves and a cycling valve connected in said system for cyclically changing the pressure in said system.
 3. Apparatus according to claim 2 in which said means connected to the sheave for applying tension includes a first supply tank, a first hydraulic pump connected to said supply tank, a first relief valve connected to said first hydraulic pump, a hydraulic cylinder connected to said pump and having a piston connected to said tensioning sheave and mounted for movement in said cylinder, a four-way valve connected to said hydraulic cylinder, said first supply tank and said first relief valve, a potentiometer mounted to be set by movement of said piston, a control valve actuated by said potentiometer and connected between said first supply tank and the connection between the first relief valve and the four-way valve.
 4. Apparatus according to claim 3 in which said hydraulic system includes a second supply tank, a second hydraulic pump connected to said second supply tank and driven by rotational movement of said Hold-back sheaves, a second relief valve connected to said second pump for providing said braking effect, and in which said cycling valve is connected to said second relief valve for cyclically by-passing said second relief valve thereby changing the braking effect.
 5. Apparatus according to claim 4 which includes a cam, a gear motor connected to said cam for rotating the cam and a cam follower on said cycling valve adapted to set the position of said cycling valve as said cam rotates.
 6. Apparatus according to claim 1 which includes means for applying heat to that part of said cable between a pair of sheaves in said series of intermediate sheaves. 